Refactor init to avoid link bugs on macOS Monterey

src/lib.rs

@@ -70,6 +70,9 @@ pub mod easy;
 pub mod multi;
 mod panic;
 
+#[cfg(test)]
+static INITIALIZED: std::sync::atomic::AtomicBool = std::sync::atomic::AtomicBool::new(false);
+
 /// Initializes the underlying libcurl library.
 ///
 /// The underlying libcurl library must be initialized before use, and must be
@@ -90,48 +93,62 @@ pub fn init() {
     /// Used to prevent concurrent or duplicate initialization.
     static INIT: Once = Once::new();
 
-    /// An exported constructor function. On supported platforms, this will be
-    /// invoked automatically before the program's `main` is called.
-    #[cfg_attr(
-        any(target_os = "linux", target_os = "freebsd", target_os = "android"),
-        link_section = ".init_array"
-    )]
-    #[cfg_attr(target_os = "macos", link_section = "__DATA,__mod_init_func")]
-    #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
-    static INIT_CTOR: extern "C" fn() = init_inner;
+    INIT.call_once(|| {
+        #[cfg(need_openssl_init)]
+        openssl_probe::init_ssl_cert_env_vars();
+        #[cfg(need_openssl_init)]
+        openssl_sys::init();
+
+        unsafe {
+            assert_eq!(curl_sys::curl_global_init(curl_sys::CURL_GLOBAL_ALL), 0);
+        }
+
+        #[cfg(test)]
+        {
+            INITIALIZED.store(true, std::sync::atomic::Ordering::SeqCst);
+        }
+
+        // Note that we explicitly don't schedule a call to
+        // `curl_global_cleanup`. The documentation for that function says
+        //
+        // > You must not call it when any other thread in the program (i.e. a
+        // > thread sharing the same memory) is running. This doesn't just mean
+        // > no other thread that is using libcurl.
+        //
+        // We can't ever be sure of that, so unfortunately we can't call the
+        // function.
+    });
+}
 
+/// An exported constructor function. On supported platforms, this will be
+/// invoked automatically before the program's `main` is called. This is done
+/// for the convenience of library users since otherwise the thread-safety rules
+/// around initialization can be difficult to fulfill.
+///
+/// This is a hidden public item to ensure the symbol isn't optimized away by a
+/// rustc/LLVM bug: https://github.com/rust-lang/rust/issues/47384. As long as
+/// any item in this module is used by the final binary (which `init` will be)
+/// then this symbol should be preserved.
+#[used]
+#[doc(hidden)]
+#[cfg_attr(
+    any(target_os = "linux", target_os = "freebsd", target_os = "android"),
+    link_section = ".init_array"
+)]
+#[cfg_attr(target_os = "macos", link_section = "__DATA,__mod_init_func")]
+#[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
+pub static INIT_CTOR: extern "C" fn() = {
     /// This is the body of our constructor function.
     #[cfg_attr(
         any(target_os = "linux", target_os = "android"),
         link_section = ".text.startup"
     )]
-    extern "C" fn init_inner() {
-        INIT.call_once(|| {
-            #[cfg(need_openssl_init)]
-            openssl_probe::init_ssl_cert_env_vars();
-            #[cfg(need_openssl_init)]
-            openssl_sys::init();
-
-            unsafe {
-                assert_eq!(curl_sys::curl_global_init(curl_sys::CURL_GLOBAL_ALL), 0);
-            }
-
-            // Note that we explicitly don't schedule a call to
-            // `curl_global_cleanup`. The documentation for that function says
-            //
-            // > You must not call it when any other thread in the program (i.e.
-            // > a thread sharing the same memory) is running. This doesn't just
-            // > mean no other thread that is using libcurl.
-            //
-            // We can't ever be sure of that, so unfortunately we can't call the
-            // function.
-        });
+    extern "C" fn init_ctor() {
+        init();
     }
 
-    // We invoke our init function through our static to ensure the symbol isn't
-    // optimized away by a bug: https://github.com/rust-lang/rust/issues/47384
-    INIT_CTOR();
-}
+    init_ctor
+};
 
 unsafe fn opt_str<'a>(ptr: *const libc::c_char) -> Option<&'a str> {
     if ptr.is_null() {
@@ -148,3 +165,20 @@ fn cvt(r: curl_sys::CURLcode) -> Result<(), Error> {
         Err(Error::new(r))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[cfg(any(
+        target_os = "linux",
+        target_os = "macos",
+        target_os = "windows",
+        target_os = "freebsd",
+        target_os = "android"
+    ))]
+    fn is_initialized_before_main() {
+        assert!(INITIALIZED.load(std::sync::atomic::Ordering::SeqCst));
+    }
+}